Distribution patterns of Anomura, Axiidea and Gebiidea (Crustacea, Decapoda) larvae at the Amazon shelf

Abstract

Taking into account the ecological relevance, the extensive coverage area of the Amazon plume and the key role of Anomura, Axiidea and Gebiidea, the present paper aims to identify the distribution patterns of the larvae of these crustaceans on the Amazon continental shelf. The samples were collected in six locations perpendicular to the coast by using superficial and oblique hauls, with a plankton net, in situations of high and low river flow and different influences of the plume when temperature, salinity and chlorophyll-a data were recorded. Different distribution patterns were observed among the taxa found along the estuary–ocean continuum, with taxa present only in estuarine and/or intermediate plume waters; taxa exclusively of outer plume and/or ocean waters, and species with no particular association being present along the transect. The highest diversity and larval abundance occurred in the outer plume, where there is a mixture of ocean water masses, more saline and high concentration of nutrients; and in sites where there is a complex reef system. Our study show that environmental variables are the main determinants of dispersion patterns, abundance and diversity of the decapod larvae in a macro-scale (>100 km). Mainly by the plume which structure the salinity gradients affecting the coastal larvae, and by nearby the Great Amazon Reef System (GARS) that can be input the marine larvae, with both behavior larval retention and export, agreeing with our initial hypotheses.